Immunogenicity Evaluation of a Rationally Designed Polytope Construct Encoding HLA-A*0201 Restricted Epitopes Derived from Leishmania major Related Proteins in HLA-A2/DR1 Transgenic Mice: Steps toward Polytope Vaccine

Abstract

BackgroundThere are several reports demonstrating the role of CD8 T cells against Leishmania species. Therefore peptide vaccine might represent an effective approach to control the infection. We developed a rational polytope-DNA construct encoding immunogenic HLA-A2 restricted peptides and validated the processing and presentation of encoded epitopes in a preclinical mouse model humanized for the MHC-class-I and II.Methods and FindingsHLA-A*0201 restricted epitopes from LPG-3, LmSTI-1, CPB and CPC along with H-2Kd restricted peptides, were lined-up together as a polytope string in a DNA construct. Polytope string was rationally designed by harnessing advantages of ubiquitin, spacers and HLA-DR restricted Th1 epitope. Endotoxin free pcDNA plasmid expressing the polytope was inoculated into humanized HLA-DRB1*0101/HLA-A*0201 transgenic mice intramuscularly 4 days after Cardiotoxin priming followed by 2 boosters at one week interval. Mice were sacrificed 10 days after the last booster, and splenocytes were subjected to ex-vivo and in-vitro evaluation of specific IFN-γ production and in-vitro cytotoxicity against individual peptides by ELISpot and standard chromium-51(51Cr) release assay respectively. 4 H-2Kd and 5 HLA-A*0201 restricted peptides were able to induce specific CD8 T cell responses in BALB/C and HLA-A2/DR1 mice respectively. IFN-γ and cytolytic activity together discriminated LPG-3-P1 as dominant, LmSTI-1-P3 and LmSTI-1-P6 as subdominant with both cytolytic activity and IFN-γ production, LmSTI-1-P4 and LPG-3-P5 as subdominant with only IFN-γ production potential.ConclusionsHere we described a new DNA-polytope construct for Leishmania vaccination encompassing immunogenic HLA-A2 restricted peptides. Immunogenicity evaluation in HLA-transgenic model confirmed CD8 T cell induction with expected affinities and avidities showing almost efficient processing and presentation of the peptides in relevant preclinical model. Further evaluation will determine the efficacy of this polytope construct protecting against infectious challenge of Leishmania. Fortunately HLA transgenic mice are promising preclinical models helping to speed up immunogenicity analysis in a human related mouse model.

A recombinant chimeric protein composed of human and mice‐specific CD4+ and CD8+ T‐cell epitopes protects against visceral leishmaniasis

“…In the light of our knowledge, the protective characteristics of these vaccine candidates could be improved by increasing the number of doses of the vaccine, the amount of peptide used in each dose and/or even using carrier molecules . In addition, the employ of vaccines combining CD4 + and CD8 + T‐cell epitopes could optimize the protective efficacy of these candidates, when compared to their individual use …”

Vaccine potential of HLA‐A2 epitopes from Leishmania Cysteine Protease Type III (CPC)

“…Recently, both the protective and therapeutic peptide‐based vaccine concepts have drawn considerable focus in the field of Leishmania . As the evidence continues to build about the role of CD8 + T cells via HLA‐A*0201, the restricted peptide in the protection might open up a new way in the battle against visceral leishmaniasis …”

Mining the Proteome of Leishmania donovani for the Development of Novel MHC Class I Restricted Epitope for the Control of Visceral Leishmaniasis

“…Some recent studies suggest that external or secreted Leishmania antigens activate CD8 + T cell in the context of HLA class I molecules [Kima et al, ; Bertholet et al, ]. Some studies also revealed a large number of potential MHC class I restricted epitopes are naturally presented to the CD8 + T cells [Stäger et al, ; Coler et al, ; Rafati et al, ; Colmenares et al, ; Iborra et al, ; Basu et al, ; Rezvan et al, ] Several authors have reported that cathepsin B like proteases are secretory proteins and are capable of eliciting CD8 + T cell response in Leishmania [Seyed et al, , ]. The knowledge of such epitopes that are capable of inducing CD8 + T cell response still needs to be explored.…”